The present invention relates in general to anti-skid devices for vehicles. More specifically, the present invention relates to a device that provides a rotatable member with links of chain, or other traction or friction increasing means, intended to be thrown sequentially under a wheel of a vehicle for increased traction between the wheel and the road surface. One device of the type generally described above is disclosed in U.S. Pat. No. 4,800,939 to Törnebäck.
The Törnebäck device utilizes an inflatable bellows to extend the movable arm that includes the pulley. It is important to note that a supply source of air for the bellows is required in order for the Törnebäck device to be operable. A suitable supply of air is likely available with larger vehicles such as semi-tractor trailers. Smaller passenger vehicles such as SUVs and trucks are not likely to have a suitable air supply. Another consideration with smaller passenger vehicles of the type described is the available space within and/or beneath the frame for securing an anti-skid device in position.
As described in the '939 patent, devices of this kind typically include a pulley provided with strands or links of chain or some other friction increasing means for sequentially positioning the chain beneath the vehicle wheel between the wheel and the road surface. Devices of this kind are not as simple to construct as would appear from the principle itself. Chains, pulleys, and other supports are, to start with, subject to very substantial forces necessitating heavy duty construction. Furthermore, a relatively large movement is required to displace the chain carrying pulley between its working position in contact with the vehicle wheel and its operative stored or stowed position. To store the pulley is particularly troublesome since different cars and passenger vehicles have different available places for the pulley. Furthermore, the pulley should be sufficiently elevated so that the chains attached to the pulley or chain wheel do not drag on the ground as this causes the links of chain to be worn prematurely. A result of the above requirements and problems that need to be solved with automatic anti-skid devices of the type described is that they are comparatively costly to produce which in turn results in a number of individuals being reluctant to obtain these safety increasing aids.
While the present invention is directed to solving some of the same problems mentioned in the '939 patent, an additional constraint has been added. This additional constraint is to design a suitable device that does not require a source or supply of air. The present invention has achieved a solution to this design challenge in a novel and unobvious manner.